60 2YC and 4YCU Geoscience Student Research Poster Showcase

This session is designed for two-year college (2YC) and four-year college and university (4YCU) students presenting research posters in any sub-discipline of geoscience.

Sunday, 19 October 2025
8:00 AM - 5:30 PM
HBGCC, Hall 1

Geology of the Kekekabic Traverse, Boundary Waters Canoe Area Wilderness, Minnesota, USA

Paper number: 60-27
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

The Kekekabic traverse, located in the Boundary Waters Canoe Area Wilderness (BWCAW) of northeastern Minnesota, contains a complex host of geologic oddities across a NNW to SSE traverse near the east end of the Kekekabic trail in Cook county. The Archean Saganaga Tonalite, part of the Wawa Terrane (2691 Ma), intrudes the Ely Greenstone (2691 Ma). The southern margin of the Saganaga tonalite includes a 1 km wide, vertical mylonitic shear zone. Ar-Ar radiometric age dating reveals the age of this mylonite to be 1.11 Ga. Deposited unconformably above the Saganaga Tonalite and Ely Greenstone shear zone is the Proterozoic Gunflint Formation, a banded iron formation (BIF). Gunflint Formation bedding along the traverse transitions from horizontal to vertical, indicating a local syncline that trends (N80°E). The SE limb of the syncline is in thrust contact with overturned Ely Greenstone best exposed atop Lookout Mountain. Farther SE, the overturned Ely Greenstone is unconformably overlain by the undeformed Gunflint Fm. which dips ~80° S. The tectonized Gunflint formation is ~100 m thick, the foliation dips steeply to the south with boudins and porphyroclasts as kinematic indicators, preserving E-W extension with top-to-the-north thrusting. Geochronological analyses using U-Pb zircon, U-Pb apatite, and Ar-Ar radiometric dating indicate that the tectonized Gunflint Formation is 1.11 Ga. The final unit exposed along the traverse is the Duluth Gabbro (1099 Ma), which dips to the south and has no fabric; it is younger than the tonalite-greenstone shear zone and the Gunflint Formation tectonite mylonites. The gabbro includes BIF xenoliths of various sizes as well as Fe-rich injectites. Therefore, a deformational event prior to the intrusion of the Duluth Gabbro occurred at 1110 Ma, a far-field shortening and metamorphic of the Grenville orogen 800 km to the east.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-413125

© Copyright 2025 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.